OPTIMAL CONTROL, VACCINATION AND AWARENESS IN TUBERCULOSIS AND HEPATITIS B VIRUS INFECTION: A QUALITATIVE CLINICAL MODELLING STUDY

Background: Tuberculosis (TB) and chronic hepatitis B virus (HBV) infection remain important causes of preventable morbidity and mortality worldwide. Mathematical models can help explore how best to combine vaccination and public awareness to reduce disease burden.

Objective: To use a transmission model to study how vaccination and public-awareness campaigns can optimally reduce the burden of TB or HBV infection, while accounting for limited resources.

Methods: In this multi-centric collaborative qualitative study, we extended a standard compartmental infectious-disease model, dividing the population into susceptible (unvaccinated), vaccinated, acutely infected, asymptomatic chronic carriers, symptomatic chronic carriers, individuals with complications and recovered. Two time-dependent control variables were introduced: intensity of vaccination and intensity of awareness activities that reduce effective contact rates. Using optimal control theory (Pontryagin’s Maximum Principle), we identified the combination of interventions over a one-year horizon that minimises both the total number of infected people and the costs of vaccination and awareness programmes. Model parameters were taken from published TB/HBV literature. Results were summarised using the basic reproduction number (R0) and numerical simulations.

Results: Without additional intervention, acute infection and chronic carrier populations increased, with a corresponding rise in severe complications. With optimal control, early aggressive use of vaccination and awareness in the first three months produced a marked increase in recovered patients and a reduction in acute and chronic infection. The model predicted that vaccination has a stronger effect than awareness campaigns on driving R0 below 1, but the combination of both strategies is more effective than either alone, especially when transmission rates are high. For plausible parameter values, R0 decreased from approximately 2.4 with no control to <1 with feasible levels of vaccination and awareness.

Conclusions: In this model, prioritising high-coverage vaccination, supported by intensive short-term awareness campaigns, is an efficient strategy to control TB or HBV transmission. These findings support existing clinical and public-health recommendations to scale up vaccination, particularly for newborns and high-risk groups, while sustaining community education on infection prevention and linkage to care.